The present invention relates to signal processing circuits in general, and, more particularly to signal processing circuits for removing angular modulation.
In many electronic systems, such as in radar and communications, angular modulation is employed to produce broadband spectrums. Pulse compression and spread-spectrum techniques are employed to spread the electromagnetic intelligence over a very large spectrum bandwidth with very little signal amplitude. If the electromagnetic energy is expanded over a very large spectrum such that it falls below the environment or receiver's noise, the information contained on the signal cannot normally be obtained. Employment of these waveforms in a system is generally referred to as a low probability of intercept system. Direction finding and location of electromagnetic emitters by electromagnetic intelligence gathering systems is denied by such low probability of intercept techniques. However, if the electromagnetic energy could be compressed into a narrow bandwidth with an enhanced signal-to-noise ratio, detection of such a signal can be performed.
Prior work in this area includes U.S. Pat. No. 3,112,452 by Kirkpatrick which discloses a signal processing arrangement in which a signal is fed to a broadband amplifier and through a plurality of filters to an adder and thence through a narrow band filter. While the patent is suitable for its intended purpose, it does not perform signal processing in the same manner as the present invention.